Dynamo action in planetesimals

星子中的发电机作用

• 批准号: 169827976
• 负责人: Professor Dr. Andreas Tilgner
• 金额: --
• 依托单位: Leibniz-Institut für Astrophysik Potsdam (AIP)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2015-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/169827976?language=en
• 关键词: Dynamo; action; planetesimals

Recent measurements of remanent magnetization in meteorites showed that the field strengths are probably incompatible with ambient field capture or impact-generated fields. The proposed mechanism for the generation of magnetic fields in meteoritic material that has formed in planetesimals is a hydromagnetic dynamo. It was also shown that fluid material must have been present in a large variety of bodies in the early Solar System. The proposed project aims at the investigation of dynamo action in planetesimals. One of the generators may be convection driven by radioactivity or chemical differentiation of the melt, providing heat sources for a few million years. Another possible dynamo mechanism may employ the nutation-driven flows in the bodies, assuming that most planetesimals had nonspherical shapes. An extreme form of dynamo with forcing on the surface could be a collisional dynamo where external, abrupt changes of the rotation axis lead to topology changes of the magnetic fields, possibly exciting a dynamo in minor bodies of the Solar System. The existence of the latter dynamo is yet to be shown theoretically. If no dynamo is found, but the field is simply amplified by differential rotation, magnetic instabilities will be important for the magnetisation of those parts of the planetesimal which had already solidified.

最近对陨石剩余磁化强度的测量表明，场强可能与环境场捕获或撞击产生的场不相容。所提出的在星子中形成的陨石材料中产生磁场的机制是水磁发电机。研究还表明，早期太阳系的多种天体中一定存在流体物质。拟议的项目旨在研究星子中的发电机作用。其中一台发电机可能是由熔体的放射性或化学分化驱动的对流，提供几百万年的热源。另一种可能的发电机机制可能采用体内章动驱动的流动，假设大多数星子具有非球形形状。表面受力的发电机的一种极端形式可能是碰撞发电机，其中旋转轴的外部突然变化导致磁场的拓扑变化，可能会激发太阳系小天体中的发电机。后一种发电机的存在尚未从理论上得到证明。如果没有找到发电机，但磁场只是通过差速旋转而放大，那么磁不稳定性对于已经凝固的星子那些部分的磁化将很重要。